The objectives of the proposed research, investigating the vibration response of the hand and arm, are: (1) Obtain information necessary to correlate the medical findings associated with Raynaud's phenomenon and other vascular- muscular disorders of the hand to the mechanical and vibration response characteristics of the hand. (2) Obtain information necessary to determine what factors should be considered when establishing hazardous vibration exposure limits to the hand for different classes of hand tools. (3) Determine the factors that influence the coupling between the hand and a hand tool handle. (4) State definite recommendations for developing hazardous vibration limit standards for vibrating hand held tools, taking into account the effects of operator size, the manner in which the tool is held, the area of the hand in which the tool is held, the percent of total area of the hand needed to hold the tool, and the size and shape of the tool handle. This objective will be met by using the mechanical impedance measurement technique to identify the system parameters describing the response characteristics of the hand and arm. The mechanical impedance is measured by directing a vibrating force into the hand and then measuring the ratio of the force to the velocity as a function of frequency. Individuals will also be asked to rate their subjective responses to the same conditions examined with the impedance tests. Then the result of the mechanical impedance tests will be correlated to the results of the subjective response test.